Astrovirus infection in hatchling turkeys: histologic, morphometric, and ultrastructural findings.

In three separate experiments, 2- or 5-day-old commercial turkey poults were inoculated orally with astrovirus and examined for clinical signs and for gross and microscopic lesions over a period of 14 days. By day 2 postinoculation (PI), inoculated poults had developed diarrhea, generalized loss of intestinal tone, and dilated ceca that contained light-yellow fluid feces and gas; these changes persisted through day 10 PI. Mild crypt hyperplasia was the only change discernible by light microscopy, and it was first noted in the proximal jejunum on day 1 PI, in the distal jejunum and ileum on day 3 PI, and in the duodenum on day 5 PI. A significant (P < 0.05) increase in crypt depth and area was documented by image analysis on day 3 PI. Ultrastructural evaluation revealed intracytoplasmic aggregates of astrovirus in enterocytes on the sides and base of villi in the ileum and distal jejunum on day 3 PI. Based on the findings, it was concluded that astrovirus caused lesions and replicated in both upper and lower segments of the small intestine in turkey poults.